1. Field of the Invention
This invention relates generally to railcars and, in particular, to an indicating mechanism for monitoring the hopper doors of a railcar.
2. Description of the Related Art
A common type of railroad freight car in use today is the freight car of the type wherein the load is discharged through hoppers in the underside of the body. Such cars are generally referred to as hopper cars and are used to haul coal, phosphate and other commodities.
After hopper cars are spotted over an unloading pit, the doors of the hoppers are opened, allowing the material within the hopper to be emptied into the pit.
Hopper cars, which may be covered, are usually found with one of two hopper configurations: transverse, in which the doors closing the hoppers are oriented perpendicular to the center line of the car; or longitudinal, in which the doors closing the hoppers are oriented parallel to the center line of the car. An example of a hopper car with transverse doors is shown in U.S. Pat. No. 5,249,531, while an example of a hopper car with longitudinal doors is shown in U.S. Pat. No. 4,224,877.
Prior art references which teach operating mechanisms for opening and closing hopper doors include U.S. Pat. Nos. 3,596,609; 4,741,274; 3,187,684; 3,611,947; 3,786,764; 3,815,514; 3,818,842; 3,949,681; 4,222,334; 4,366,757; 4,601,244; 5,823,118; and 5,249,531. There are several disadvantages to the hopper door operating mechanisms described in some of the aforementioned patents. One problem is that some of the prior art mechanisms are designed such that each actuating mechanism is connected to doors from two separate hoppers. Thus, if the mechanism fails, it effects the operation of two hoppers. Another disadvantage of some of the above described hopper door mechanisms is that the operating mechanisms limit the distance of the door motion, thus limiting the open area of the car's bottom. This arrangement slows the unloading process and causes additional costs and potential damage to the car due to increased periods in thaw sheds. However, many of these systems usually require automatic operation of the doors, which requires an operating cylinder and valving.
When using automatic door operating systems, it is important to be certain that the doors are fully closed. Many automatic door systems are designed with an overcenter latch to insure that the doors will not inadvertently open, as this could cause serious injury and/or damage to occur.
One problem which may occur with an operating cylinder is a condition in which the air cylinder is leaking, allowing the movable shaft within the cylinder to falsely indicate the actual state of the cylinder (activated or deactivated).
Another potential disadvantage of using an air cylinder operating door system is that the air cylinder is usually physically located where it is difficult to actually observe the movement of the movable shaft actuating the hopper doors.